Dual display apparatus and method of driving the same

ABSTRACT

A dual display including: a first display for displaying first visual information and receiving a touch input; a second display including a double-sided emission display for displaying second visual information through a first surface or a second surface opposite to the first surface, and receiving a touch input; a sensor for sensing relative locations of the first and second displays; and a controller for determining whether or not the second display is covering the first display according to a signal of the sensor, and for controlling the first and second displays. Here, the controller is configured to receive the touch input from the second display when the second display unit covers the first display, and to receive the touch input from the first display when the second display does not to cover the first display.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/685,656, filed Nov. 26, 2012, which claims priority to and thebenefit of Korean Patent Application No. 10-2012-0055531, filed May 24,2012, the entire content of both of which is incorporated herein byreference.

BACKGROUND

1. Field

Embodiments of the present invention relate to a dual display apparatusand a method of driving the dual display apparatus.

2. Description of the Related Art

Display apparatuses capable of replacing cathode ray tubes have beenrecently been developed. These display apparatuses include liquidcrystal displays (LCDs), field emission displays (FEDs), plasma displaypanels (PDPs), electro-luminescence (EL) display apparatuses, and thelike.

Among the above display apparatuses, PDPs, which have simple structuresand manufacturing processes, are recognized as being display apparatusesthat make simple and large displays, however, they have low emissionefficiency and brightness and high power consumption. Comparatively,active LCDs, to which thin film transistors (TFTs) are applied asswitching devices, use semiconductor processes, and are used as smalland large display devices. On the other hand, LCDs have high powerconsumption due to backlight units. Also, in LCDs, a large amount ofoptical loss occurs due to optical devices such as polarizing filters,prism sheets, diffusion plates, and the like, and viewing angles may berelatively narrow.

EL display apparatuses are largely classified into inorganic EL displayapparatuses and organic EL display apparatuses according to materials ofemission layers, and are self-emitting apparatuses (i.e., they emitlight by themselves). EL display apparatuses have a fast response speed,high emission efficiency and brightness, and wide viewing angles. Amongthese EL display apparatuses, organic EL display apparatuses includingorganic light emitting diodes (OLEDs) have a low direct current drivingvoltage, form a thinner display, emit light uniformly, easily formpatterns, have a high emission efficiency, emit substantially all colorsin a visible spectrum, and the like, and thus EL apparatuses includingOLEDs are undergoing the most active research with respect toapplications of display apparatuses.

Furthermore, EL display apparatuses have a fast screen response speed,wide viewing angles, better color expression than LCDs, flexiblecharacteristics, and are applicable to a wide variety of applications.Thus, EL display apparatuses have been used as display panels ofportable electronic products such as cellular phones, PDAs, etc. anduser demand for EL display apparatuses is increasing in terms of largescreens and various usages of large screens of portable electronicproducts.

SUMMARY

Embodiments of the present invention provide for a dual displayapparatus and a method of driving the dual display apparatus.

According to an aspect of the present invention, there is provided adual display apparatus including: a first display configured to displayfirst visual information and to receive a touch input; a second displayincluding a double-sided emission type display configured to displaysecond visual information through a first surface or a second surfaceopposite to the first surface, and to receive a touch input; a sensorconfigured to sense relative locations of the first display and thesecond display; and a controller configured to determine whether thesecond display is covering the first display or is not covering thefirst display according to a signal of the sensor, and configured tocontrol the first display and the second display. Here, the controlleris configured to receive the touch input from the second display whenthe second display unit covers the first display, and to receive thetouch input from the first display when the second display does not tocover the first display.

The second display may include an organic light emitting display that issubstantially transparent.

One side of the second display may be coupled (e.g., connected) to thefirst display so that the second display is configured to rotate andmove with respect to the first display.

In an embodiment, the sensor includes: a first sensor at one side of thefirst display; and a second sensor at one side of the second display,wherein the controller is configured to calculate an angle between thefirst display and the second display according to signals received fromthe first sensor and the second sensor.

The first sensor and the second sensor may include gyro sensors.

In an embodiment, the controller is configured to activate one of thefirst display or the second display and to inactivate the other one ofthe first display or the second display that is not activated when thesecond display covers the first display, and to activate both the firstdisplay and the second display when the second display does not coverthe first display.

The controller may be configured to inactivate the first display, toactivate the second display, and to control the second display todisplay menu icons when the second display covers the first display.

The dual display apparatus may further include: a sound sensorconfigured to sense a sound signal for controlling the dual displayapparatus, according to an embodiment of the present invention.

The controller may be configured to activate the first display, toinactivate the second display, and to control the sound sensor to beactivated when the second display covers the first display.

The controller may be configured to activate the first display and thesecond display to output third visual information, which is obtained byoverlapping the first visual information and the second visualinformation, to a user when the second display covers the first display.

According to another aspect of the present invention, there is provideda method of driving a dual display apparatus, the method including:detecting relative locations of a first display and a second display;determining whether or not the second display, which includes asubstantially transparent portion, is covering the first display; if itis determined that the second display is covering the first display,activating at least one of the first display or the second display; andif it is determined that the second display is covering the firstdisplay, receiving a sound signal or a touch signal.

The activating of the at least one of the first display or the seconddisplay may include: activating the first display and inactivating thesecond display so that first visual information that is output throughthe first display is output to a user through the substantiallytransparent portion of the second display.

The receiving of the sound signal or the touch signal may include:receiving the sound signal for controlling the dual display apparatus.

The activating of the at least one of the first display or the seconddisplay may include: inactivating the first display and activating thesecond display.

The receiving of the sound signal or the touch signal may include:receiving the touch signal for controlling the dual display apparatusthrough a second surface of the second display opposite to a firstsurface that faces the first display.

The activating of the at least one of the first display or the seconddisplay includes: displaying menu icons through the second display,according to an embodiment.

The activating of the at least one of the first display and the seconddisplay may include: activating the first display that outputs firstvisual information; and activating the second display that outputssecond visual information.

In an embodiment, the first visual information and the second visualinformation may overlap at least partially to form third visualinformation.

The receiving of the sound signal or the touch signal may include:receiving the touch signal for controlling the dual display apparatusthrough a second surface of the second display opposite to a firstsurface thereof that faces the first display.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and aspects of the present invention willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a schematic perspective view of a dual display apparatus,according to an embodiment of the present invention;

FIG. 2 is a schematic block diagram of a dual display apparatus,according to an embodiment of the present invention;

FIG. 3 is a schematic flowchart of driving a dual display apparatus,according to an embodiment of the present invention;

FIG. 4 illustrates a driving status of a dual display apparatus in whicha first display unit and a second display unit overlap each other,according to an embodiment of the present invention;

FIG. 5 illustrates a driving status of a dual display apparatus in whicha first display unit and a second display unit overlap each other,according to an embodiment of the present invention; and

FIG. 6 illustrates a driving status of a dual display apparatus in whicha first display unit and a second display unit do not overlap eachother, according to an embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, certain exemplary embodiments according to the presentinvention are described in detail with reference to the accompanyingdrawings. However, these exemplarily embodiments are not intended tolimit the present invention to particular modes of practice, and it willbe appreciated that all changes, equivalents, and substitutes that donot depart from the spirit and scope of the present invention areencompassed in the present invention. In the description of the presentinvention, certain detailed explanations may be omitted when it isdeemed that they may unnecessarily obscure certain aspects of theinvention. The terms used in the present specification are merely usedto describe particular embodiments, and are not intended to limit thepresent invention. An expression used in the singular encompasses theexpression of the plural, unless it has a clearly different meaning inthe context. In the present specification, it is to be understood thatthe terms such as “including” or “having,” etc., are intended toindicate the existence of the features, numbers, steps, actions,components, parts, or combinations thereof disclosed in thespecification, and are not intended to preclude the possibility that oneor more other features, numbers, steps, actions, components, parts, orcombinations thereof may exist or may be added. While such terms as“first,” “second,” etc., may be used to describe various components,such components must not be limited to the above terms. The above termsare used only to distinguish one component from another. As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items. Expressions such as “at least one of,” whenpreceding a list of elements, modify the entire list of elements and donot modify the individual elements of the list.

FIG. 1 is a schematic perspective view of a dual display apparatus 100,according to an embodiment of the present invention. FIG. 2 is aschematic block diagram of the dual display apparatus 100, according toan embodiment of the present invention.

Referring to FIGS. 1 and 2, the dual display apparatus 100 according toan embodiment of the present invention includes a first display unit 110(first display), a second display unit 120 (second display), a touchrecognizing unit 130 (touch sensor), a sensing unit 140 (sensor), asound recognizing unit 150 (sound sensor), and a control unit 160(controller).

The first display unit 110 may output image information through onesurface thereof. The first display unit 110 may be a liquid crystaldevice or an organic light emitting display device. The first displayunit 110 may recognize a touch. For example, a first touch recognizingunit 131 capable of recognizing a touch input by a user's finger or byusing an external input apparatus, such as, a stylus pen, may beincluded (e.g., integrally formed) with the first display unit 110. Thefirst touch recognizing unit 131 may recognize an external touch inputby using a resistive method, a capacitive method, or any other suitablemethod.

In an embodiment, the second display unit 120 outputs the imageinformation through a first surface 121 thereof facing the first displayunit 110 and/or a second surface 122 opposite to the first surface 121(i.e. a double-sided emission type display). The second display unit 120may be a transparent display (or a substantially transparent display, atranslucent display, a not fully opaque display, or the like). Thus, ina case where the second display unit 120 covers the first display unit110, a screen of the first display unit 110 may be viewed (recognized)by a user through the transparent second display unit 120.

The second display unit 120 may recognize the touch (e.g., the touchinput by the user). For example, a second touch recognizing unit 132capable of recognizing the touch input by the user's finger or by usingthe external input apparatus, such as, the stylus pen, may be included(e.g., integrally formed) with the second display unit 120. As anexample, the second touch recognizing unit 132 may be formed in bothsurfaces of the second display unit 120 to recognize a touch input ofthe first surface 121 of the second display unit 120 and recognize atouch input of the second surface 122 thereof. The second touchrecognizing unit 132 may recognize the external touch input by using,for example, the resistive method or the capacitive method (similar tothe first touch recognizing unit 131).

In an embodiment, one side of the second display unit 120 is coupled tothe first display unit 110 so that the second display unit 120 mayrotate and move with respect to the one side coupled to the firstdisplay unit 110. According to the rotation and movement of the seconddisplay unit 120 with respect to the one side thereof, the seconddisplay unit 120 may be disposed to overlap a screen of the firstdisplay unit 110 (an overlap position) or may not be disposed to overlapa screen of the first display unit 110 (a non-overlap position). Thatis, the second display unit 120 is capable of being disposed at theoverlap position and may alternatively be disposed at the non-overlapposition according to the rotation and movement of the second displayunit 120 with respect to the one side thereof.

In an embodiment, the sensing unit 140 senses whether or not the seconddisplay unit 120 is disposed at the overlap position or the non-overlapposition. The second display unit 120, having one side fixed, rotateswith respect to the first display unit 110. In this regard, the sensingunit 140 may determine whether or not the second display unit 120 isdisposed to overlap the screen of the first display unit 110 byobtaining a relative movement of the second display unit 120 withrespect to the first display unit 110, i.e. a level of rotation of thesecond display unit 120.

The sensing unit 140 may include a first sensor 141 disposed at one sideof the first display unit 110 and a second sensor 142 disposed at oneside of the second display unit 120. As an example, the first sensor 141and the second sensor 142 may be formed to face each other (e.g., faceeach other when the second display unit is disposed at the overlapposition). The first sensor 141 and the second sensor 142 may includegyro sensors so as to sense an angle or an angle variation of the seconddisplay unit 120 that changes with respect to the first display unit110.

In an embodiment, the sound recognizing unit 150 is included in the dualdisplay apparatus 100 in such a way that the dual display apparatus 100may be driven according to a sound command of a user. The soundrecognizing unit 150 may be driven according to relative locations ofthe first display unit 110 and the second display unit 120. As describedabove, the first display unit 110 and the second display unit 120including the first touch recognizing unit 131 and the second touchrecognizing unit 132, respectively, may recognize touch inputs and,thus, the dual display apparatus 100 may be driven. However, it may beimpractical or impossible to input a touch through the first touchrecognizing unit 131 formed in the first display unit 110 when the firstdisplay unit is covered by the second display unit 120. In this case,the sound recognizing unit 150 may be activated so that the dual displayapparatus 100 may be driven according to the sound command of the user.

In an embodiment of the present invention, the control unit 160 isincluded (e.g., embedded) in the dual display apparatus 100, detects therelative locations of the first display unit 110 and the second displayunit 120 based on sensing information transferred from the sensing unit140, and accordingly controls driving of the dual display apparatus 100.A detailed operation of the control unit 160 and resultant driving ofthe dual display apparatus 100 will be described with reference to FIGS.3 and 6.

FIG. 3 is a schematic flowchart of driving of the dual display apparatus100, according to an embodiment of the present invention. The dualdisplay apparatus 100 is driven according to a control operation of thecontrol unit 160. FIGS. 4 through 6 illustrate driving statuses of thedual display apparatus 100 with respect to relative locations of thefirst display unit 110 and the second display unit 120 according toembodiments of the present invention. FIGS. 4 and 5 illustrate drivingstatuses of the dual display apparatus 100 in which the second displayunit 120 is disposed at an overlap position, i.e., the first displayunit 110 and the second display unit 120 overlap each other. FIG. 6illustrates a driving status of the dual display apparatus 100 in whichthe second display unit 120 is disposed at a non-overlap position, i.e.,the first display unit 110 and the second display unit 120 do notoverlap each other.

Referring to FIG. 3, in operation S11, relative locations of the firstdisplay unit 110 and the second display unit 120 are detected. Thecontrol unit 160 may detect the relative operations of the first displayunit 110 and the second display unit 120 by receiving respective signalssensed by the first sensor 141 and the second sensor 142. The controlunit 160 may then determine whether or not the first display unit 110and the second display unit 120 overlap each other by detecting an anglebetween the first display unit 110 and the second display unit 120 basedon, for example, sensing values of a gyro sensor included in the firstsensor 141 and a gyro sensor included in the second sensor 142. Theangle between the first display unit 110 and the second display unit 120may be detected by integrating angular speeds sensed by the first sensor141 and the second sensor 142. To prevent an error from occurring indetecting the angle between the first display unit 110 and the seconddisplay unit 120, an acceleration sensor may be used with the gyrosensor.

In operation S12, the control unit 160 determines whether the seconddisplay unit 120 covers the first display unit 110. The control unit 160determines whether the second display unit 120 covers the first displayunit 110 based on a result of the detection in operation S11. The seconddisplay unit 120 may be disposed at the overlap position or thenon-overlap position. In respective cases, the control unit 160 may havedifferent operations for controlling the dual display apparatus 100 andmethods of recognizing a user command. The case where the second displayunit 120 covers the first display unit 110 will now be described.

In operation S13, the control unit 160 identifies a program beingexecuted in the dual display apparatus 100. When the second display unit120 covers the first display unit 110, since the control unit 160 maycontrol driving of the first display unit 110 and the second displayunit 120 according to the program being executed in the dual displayapparatus 100, the control unit 160 first identifies the program beingexecuting in the dual display apparatus 100. If the program beingexecuted in the dual display apparatus 100 requires driving of both thefirst display unit 110 and the second display unit 120, operation S20 isperformed. If the program being executed in the dual display apparatus100 does not require driving of both the first display unit 110 and thesecond display unit 120, operation S30 or S40 is performed.

A case where operation S20 is performed will now be described. OperationS20 includes operations S21 and S22, according to an embodiment of thepresent invention.

In operation S21, the control unit 160 activates both the first displayunit 110 and the second display unit 120. As an example of a case wherethe program being executed in the dual display apparatus 100 requiresdriving of both the first display unit 110 and the second display unit120 is where both first visual information I1 and second visualinformation I2 need to be output through the first display unit 110 andthe second display unit 120, respectively, to the user. An example ofoutputting both the first visual information I1 and the second visualinformation I2 is illustrated in FIG. 4 by a program “putting clotheson”.

More specifically, referring to FIG. 4, an image (the first visualinformation I1) of the user is output through the first display unit110, and an image (the second visual information I2) of clothes that maybe purchased by the user is output through the second display unit 120,and thus the user who uses the dual display apparatus 100 may recognizean image (third visual information I3 obtained by overlapping the firstvisual information I1 and the second visual information I2) of the userwearing the clothes.

As described above, in a case where a program for determining whetherclothes suit the user before the user purchases the clothes operates,the control unit 160 may activate both the first display unit 110 andthe second display unit 120. The first visual information I1 and thesecond visual information I2 may be output through the first displayunit 110 and the second display unit 120, respectively, and then theuser may recognize the third visual information I3 obtained byoverlapping the first visual information I1 and the second visualinformation I2.

Although the image of the user wearing the clothes is provided as thethird visual information I3 through the dual display apparatus 100 byoutputting the image of the user corresponding to the first visualinformation I1 and the image of clothes corresponding to the secondvisual information I2 in the present embodiment, the present inventionis not limited thereto. For example, in another embodiment, first visualinformation I1 is output through the first display unit 110, and secondvisual information having a different size from the first visualinformation I1 or disposed slightly obliquely while being similar to thefirst visual information I1 is output through the second display unit120, and thus third visual information having a cubic effect andobtained by overlapping the first visual information and the secondvisual information may be provided to the user.

In operation S22, a user command may be received through a touch. Forexample, a user touch input may be recognized by activating the secondtouch recognizing unit 132 in (e.g., formed in) the second surface 122of the second display unit 120. The second display unit 120 is disposedat the overlap position and receives a touch signal through the secondsurface 122 thereof, and thus the user may drive the dual displayapparatus 100 through an intuitive touch input.

Next, a case where operation S30 is performed will now be described.Operation S30 includes operations S31 and S32, according to anembodiment of the present invention.

Operation S30 is performed when the program being executed in the dualdisplay apparatus 100 does not require driving of both the first displayunit 110 and the second display unit 120, for example, when a homescreen is being executed, or the first visual information I1 and thesecond visual information I2 do not need to be simultaneously (orconcurrently) output such as when a news search is being performed.

In operation S31, the control unit 160 may activate the second displayunit 120 and inactivate the first display unit 110. If the first displayunit 110 is inactivated, a screen of the first display unit 110 may beblacked out, and the second display unit 120 may output the secondvisual information I2.

For example, referring to FIG. 5, menu icons M1, M2, M3, and M4 (whichmay be higher than a specific priority level) are displayed on thesecond display unit 120 (at least one of the menu icons M1, M2, M3, andM4 that are higher than the specific priority level may be displayed onthe second display unit 120). The user may select and set the menu iconsM1, M2, M3, and M4 (e.g., the menu icons that are higher than thespecific priority level) in advance.

In operation S32, a user command may be received through a touch. Forexample, a user touch input may be recognized by activating the secondtouch recognizing unit 132 in (e.g., formed in) the second surface 122of the second display unit 120. The second display unit 120 overlaps thefirst display unit 110 and receives a touch signal through the secondsurface 122 thereof, and thus the user may drive the dual displayapparatus 100 through an intuitive touch input.

Next, a case where operation S40 is performed will now be described.Operation S40 includes operations S41 and S41, according to anembodiment of the present invention.

Operation S40 is performed when the program being executed in the dualdisplay apparatus 100 does not require driving of both the first displayunit 110 and the second display unit 120, for example, when a homescreen is being executed, or the first visual information I1 and thesecond visual information I2 do not need to be simultaneously (orconcurrently) output such as when a news search is being performed.

In operation S41, the control unit 160 activates the first display unit110 and inactivates the second display unit 120. If the second displayunit 120 is inactivated, the second display unit 120 does not output thesecond visual information I2, and the first visual information I1 outputthrough the first display unit 110 may pass through the transparentsecond display unit 120 and may be viewed (e.g., recognized) by theuser.

Although the menu icons M1, M2, M3, and M4 that are higher than thepriority level may be displayed on the second display unit 120 asdescribed above with reference to FIG. 5, menu icons that are higherthan a priority level may be displayed on the first display unit 110,are capable of being seen through the transparent second display unit120, and be visually recognized by the user in another embodiment.

In operation S42, a user command may be received through sound. Forexample, although the second display unit 120 is disposed at the overlapposition, when the second display unit 120 is inactivated, the secondtouch recognizing unit 132 may also be inactivated, which makes itdifficult to recognize a user touch input even if the second surface 122of the second display unit 120 is touched. In this case, the user soundcommand may be recognized by activating the sound recognizing unit 150.The user sound command may be input into the control unit 160 throughthe sound recognizing unit 150. The control unit 160 may control drivingof the dual display apparatus 100 according to the recognized soundcommand.

As described above, in operation S12, the control unit 160 determineswhether or not the second display unit 120 covers the first display unit110 based on the detection of operation S11 (also described above). Thecase where the second display unit 120 does not cover the first displayunit 110, that is the second display unit 120 is disposed at thenon-overlap position will now be described in reference to operationS50. S50 includes operations S51 and S52, according to an embodiment ofthe present invention.

In operation S51, the control unit 160 activates both the first displayunit 110 and the transparent second display unit 120. The first visualinformation I1 output through the activated first display unit 110 andthe second visual information I2 output through the activated seconddisplay unit 120 may be different visual information.

For example, referring to FIG. 6, a screen that runs a web browser maybe output as the first visual information I1 through the first displayunit 110, and a virtual keyboard for inputting a keyword into the webbrowser may be output as the second visual information I2 through thesecond display unit 110.

In operation S52, a user command may be received through a touch input.A user touch input may be recognized through the first touch recognizingunit 131 and/or the second touch recognizing unit 132 in (e.g., formedin) the first display unit 110 and the second display unit 120,respectively. Recognition of touch signals of the first touchrecognizing unit 131 and the second touch recognizing unit 132, andoutputting of visual information of the first display unit 110 and thesecond display unit 120 may be performed separately or in combination.

In an embodiment, the second display unit 120 outputs a plurality ofmenu icons, and the first display unit 110 outputs a screen that runsone of the menu icons output by the second display unit 120. In thiscase, if the user touches the screen output by the first display unit110, the first touch recognizing unit 131 receives the touch input sothat visual information according to the touch input may be outputthrough the first display unit 110. If the user touches one of the menuicons output by the second display unit 120, the second touchrecognizing unit 132 in (e.g., formed in) the first surface 121 of thesecond display unit 120 may receive the touch input so that a screenthat runs the touch menu icon may be output through the second displayunit 120. Recognition of touch signals by the first touch recognizingunit 131 and the second touch recognizing unit 132 and outputting ofvisual information of the first display unit 110 and the second displayunit 120 may be separately performed.

In another embodiment the second display unit 120 outputs a plurality ofmenu icons, and the first display unit 110 outputs a screen that runsone of the menu icons output by the second display unit 120. If the usertouches one of the menu icons output by the second display unit 120, thesecond touch recognizing unit 132 in (e.g., formed in) the first surface121 of the second display unit 120 may receive the touch input so that ascreen that runs the touch menu icon may be output through the firstdisplay unit 110. Recognition of touch signals of the first touchrecognizing unit 131 and the second touch recognizing unit 132 andoutput of visual information of the first display unit 110 and thesecond display unit 120 may be performed in combination.

In another embodiment, recognition of touch signals by the first touchrecognizing unit 131 and the second touch recognizing unit 132 andoutputting of visual information of the first display unit 110 and thesecond display unit 120 may be performed in combination as follows.

For example, as shown in FIG. 6, the screen that runs the web browser isoutput through the first display unit 110. In this regard, in a casewhere the user touches a search window on the screen output by the firstdisplay unit 110, the first touch recognizing unit 131 receives the usertouch input and transfers the user touch input to the control unit 160.

The control unit 160 controls the second display unit 120 to output avirtual keyboard screen for inputting a search word based on a receivedsignal. If the user touches the virtual keyboard screen output by thesecond display unit 120, the second touch recognizing unit 132 receivesthe user touch input and transfers the user touch input to the controlunit 160. The control unit 160 may display the search word on the searchwindow of the first display unit 110 according to a touched keyboard.

As described above, according to an embodiment of the present invention,a user command may be recognized in various ways, and various types ofvisual information may be output according to relative locations of afirst display unit and a transparent second display unit.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. A dual display apparatus comprising: a firstdisplay configured to display first visual information and comprising afirst touch unit; a second display comprising: a second touch unit; anda transparent display configured to display second visual informationand comprising a first surface and a second surface opposite to thefirst surface; a sensor configured to sense relative locations of thefirst display and the second display; and a controller configured todetermine whether or not the second display is covering the firstdisplay according to a signal of the sensor, and configured to controlthe first display and the second display, wherein the sensor comprises:a first sensor at one side of the first display to face the seconddisplay when the second display covers the first display; and a secondsensor at one side of the second display to face the first display whenthe second display covers the first display, and wherein the controlleris configured to detect an angle between the first display and thesecond display according to signals received from the first sensor andthe second sensor.
 2. The dual display apparatus of claim 1, wherein thetransparent display comprises a double-sided emission type display. 3.The dual display apparatus of claim 1, wherein the controller is furtherconfigured to receive a touch input from the second display when thesecond display covers the first display, and to receive a touch inputfrom the first display when the second display does not cover the firstdisplay.
 4. The dual display apparatus of claim 1, wherein the secondtouch unit is on the first and second surfaces of the transparentdisplay.
 5. The dual display apparatus of claim 1, wherein the seconddisplay is coupled to the first display and configured to rotate andmove with respect to the first display.
 6. The dual display apparatus ofclaim 1, wherein the first sensor and the second sensor comprise gyrosensors.
 7. The dual display apparatus of claim 1, wherein thecontroller is further configured to activate one of the first display orthe second display and to inactivate another one of the first display orthe second display when the second display covers the first display, andconfigured to activate both the first display and the second displaywhen the second display does not to cover the first display.
 8. The dualdisplay apparatus of claim 7, wherein the controller is furtherconfigured to inactivate the first display, to activate the seconddisplay, and to control the second display to display menu icons whenthe second display covers the first display.
 9. The dual displayapparatus of claim 1, further comprising: a sound sensor configured tosense a sound signal for controlling the dual display apparatus.
 10. Thedual display apparatus of claim 9, wherein the controller is furtherconfigured to activate the first display, to inactivate the seconddisplay, and to control the sound sensor to be activated when the seconddisplay covers the first display.
 11. The dual display apparatus ofclaim 1, wherein the controller is further configured to activate thefirst display and the second display to output third visual informationby overlapping the first visual information and the second visualinformation when the second display covers the first display.